struct FvtToolbar: ViewModifier {
    var title: String
    var rightTitle: String
    var rightAction: ()->()

    func body(content: Content) -> some View {
        content
            // 进一步定制工具栏外观行为...
    }

    init(_ title:String, _ rightTitle:String, _ rightAction:@escaping ()->()){
        self.title = title 
        self.rightTitle = rightTitle 
        self.rightAction = rightAction 
    }
}